centre text in a

I have this HTML
<a href="note.pdf">NOTE</a>
and this related CSS
a {
display: block;
width: 172px;
height: 28px;
font-size: 0.7em;
color: darkblue;
text-align: center;
text-decoration: none;
background-color: white;
border: 1px solid #6FA0CC;
border-radius: 14px;
}
Vertically the text in the anchor appears above centre. Is it possible
to get the text to centre vertically with just CSS or do I need to first
wrap the text in, say, a span?
Andrew Poulos